Electrical gas-blast switch

ABSTRACT

In a gas-blast switch with a compression device to produce a quenching gas blast, in order to make the magnetic effect of the break current available already at the beginning of the cut-off movement, a compression chamber and a piston-cylinder system form an energy accumulator. A movable element of the piston-cylinder system is mechanically linked with an armature, which is axially moved by the magnetic field of a stator, which field is excited by the break current. The armature and the stator are arranged in such a way that the magnetic field already causes the armature to move.

FIELD OF THE INVENTION

The present invention relates to an electrical gas-blast switch.

BACKGROUND INFORMATION

German Patent Application Nos. 40 10 006 and 40 10 007 describegas-blast switches which include a switching piece which can be moved bya drive, which connects a fixed contact piece with a connector piecethrough which load current flows in the cut-in state (cut-in position).The compression device in such gas-blast switches includes a compressionpiston and a compression cylinder which enclose a compression space.During the cut-off process, the piston and the cylinder are movedrelative to one another. Any quenching gas located in the compressionspace is thus compressed, and serves to blast the arc which occurs whenthe switching piece moves away from the contact piece. SF₆, for example,is used as the quenching gas. In order to utilize the magnetic effect ofthe cut-off or short-circuit current to support the drive, the contactarrangement is partially surrounded by a stator which consists offerromagnetic material and has at least one continuous slit. Thecompression cylinder shown in German Application No. 40 10 006 or thecompression piston shown in German Application No. 40 10 007 each has atleast one rod-shaped armature. Only after a partial movement of thecompression cylinder during the cut-off process does the armature getinto the region of influence of the magnetic field of the stator excitedby the break current, which draws the armature into the slit of thestator, supporting the drive. The drive-supporting axial movement of thearmature, which does not start until after the beginning of thecompression cylinder movement, is therefore not available for theinitial acceleration of the compression cylinder.

In another known gas-blast switch illustrated in German Patent No. 31 41324, the rated current flows via the compression cylinder. During thecut-off process, the break current commutates to a gradient coil after acertain movement distance of the cylinder, and causes the movement of aring piston which directly supports the arc blasting.

Another gas-blast switch is described in U.S. Pat. No. 4,438,308 whichdescribes a gas-blast switch in which an auxiliary blast effect due tocontraction of the spring windings as a result of the break current onlystarts after the compression cylinder has been significantly moved by adrive.

SUMMARY OF THE INVENTION

The present invention provides a gas-blast switch which includes acontact arrangement which includes a fixed contact piece, a connectorpiece and a switching piece which can be moved by a drive, with acompression device to produce a blast of quenching gas. The gas-blastswitch also includes a compression piston and a compression cylinderwhich can be moved relative to one another by the drive during thecut-off process, starting from a cut-in position, and a stator which canbe excited by the break current, the magnetic field of which causes adrive-supporting axial movement of at least one armature.

An object of the present invention is to provide a gas-blast switch inwhich the magnetic effect of the break current is already almostcompletely available, particularly at the beginning of the cut-offmovement of the compression cylinder, and which allows a rapid switchingmovement with a comparatively slight necessary drive power.

The aforementioned object is accomplished according to the presentinvention with a gas-blast switch having an energy accumulator in theform of a compression chamber where a piston/cylinder system isprovided, the movable element of which is mechanically linked with thearmature. The armature and the stator are arranged in such a way thatthe magnetic field already causes the armature to move in the cut-inposition, and that the energy accumulator is arranged in such a way thatdischarge of the energy accumulator acts to support the drive. The(short-circuit) current, which is significantly increased, for example,in case of a short-circuit, causes an armature movement even before thegas-blast switch is triggered and before the switching piece and thecompression cylinder start to move, resulting in a volume reduction ofthe compression chamber. The compression cylinder therefore forms apneumatic energy accumulator. A significant advantage of the presentinvention consists of the fact that the energy accumulator is chargedeven before the switch is triggered, so that the energy accumulated atthe time of triggering is completely available to support the drive. Theacceleration energy required for the moving switch parts at thebeginning of the cut-off process can be advantageously made available bythe energy accumulator, for the most part, so that the drive can becost-effectively sized for a comparatively low total power. The switchaccording to the present invention can switch relatively quickly.

In another embodiment of the present invention, the energy accumulatoris arranged within the compression cylinder.

Yet in another embodiment of the present invention, the energyaccumulator is arranged within the connector piece and the side of thecompression chamber which faces away from the contact arrangement formedby a power take-off piston which is mechanically linked with the drive.With this structure of the present invention, the armature can servedirectly as a drive piston of the compression chamber. For advantageousadaptation to the necessary stroke and force requirement, the drivepiston and the power take-off piston can have different cross-sections.Therefore the compression chamber advantageously forms a stroke andforce converter.

To increase the magnetic flux and thereby increase the utilization ofthe magnetic effect of the break current, still another embodiment ofthe present invention provides that the stator is a coil. A preferredembodiment of the present invention includes the coil consisting of asegment of the connector piece, the wall of which having a radial slitwound like a screw passing through it.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of a gas-blast switch according to thepresent invention in the cut-in position.

FIG. 2 shows a cross-section along line II--II in FIG. 1.

FIG. 3 shows another embodiment of the gas-blast switch according to thepresent invention.

DETAILED DESCRIPTION

As shown in FIG. 1, a gas-blast switch in accordance with a presentinvention has a contact arrangement 1 with a fixed contact piece 2, aconnector piece 3 which lies coaxially opposite the fixed contact piece2, through which load current flows, and a movable switching piece 5.The movable switching piece 5 is rigidly connected with a compressioncylinder 6. The compression cylinder 6, together with a fixedcompression piston 7 and a filler element 8, forms a mechanicalcompression device 10 for a quenching gas 11. The compression cylinder 6is connected with a mechanical drive 13, via a switching rod 16 (whichis not shown with detail.) Parts of a rod 14 and a fork 15 are shown inFIG. 1. The connector piece 3, towards which the compression cylinder 6moves during a cut-off movement, in the direction of the arrow A, issurrounded by two approximately semicircular yokes 20 and 21,approximately 90 mm high (FIG. 2). Guide shafts are formed between theirpole surfaces 20a, 20b and 21a, 21b which hold two armatures 23 and 24.Two conductors 27, 28 through which the rated current, i.e. the breakcurrent flows in the same direction, are arranged in the center region26 of the yokes 20 and 21. This arrangement, together with the yokes 20and 21, forms a stator 29 for the armatures 23 and 24.

The armatures 23 and 24 are connected with a ring piston 32 viaconnecting rods 30 and 31. The piston 32 delimits a compression chamber34, which is closed off by the compression cylinder 6 on the outside andby a guide part 36 on the inside and the bottom. The piston/cylindersystem 32, 36, 6 forms a pneumatic energy accumulator 37. FIG. 1illustrates the gas-blast switch in the "cut-in position" 38.

If a short-circuit occurs, the load current (short-circuit current)increases before the switch is triggered, to the point that a magneticfield of the stator 29 is formed which is strong enough so that thearmatures 23 and 24 come into its region of effect and are pulledbetween the guide shafts (pole surfaces) 20a, 21a and 20b, 21b of thestator 29. The piston 32 which is rigidly connected with the armatures23 and 24 via the connecting rods 30 and 31 is accordingly moved in thedirection of the arrow A, compressing the quenching gas located in thecompression chamber 34. The movement of the piston 32 ends before theswitch is triggered, i.e. before the compression cylinder 6 is releasedand moved in the direction of the arrow A by the drive 12, via theswitching rod 16. At the beginning of the cut-off movement of thecompression cylinder, the pneumatic energy stored in the compressionchamber 34 is therefore available. The compression chamber excesspressure, which has a strong drive-supporting effect during the initialmovement (acceleration) of the compression cylinder 6 and any otherswitch parts, acts on the bottom region of the guide part 36, so thatrapid switching is possible with a relatively low drive power.

In order to bring the piston 32 back into its initial position after thecut-off process, when current cut-in occurs again, positioning pressuresprings 40a, 40b surround the connecting rods 30, 31.

FIG. 3 shows another embodiment of a gas-blast switch according to thepresent invention which is modified with regard to the armaturearrangement and the stator. The gas-blast switch is shown in FIG. 3 inthe cut-in position 38. An armature 50 is movable in the direction of arear flange 55, inside a guide tube 52 which is lined with insulationmaterial 51, counter to the force of a positioning spring 53. With itsend 56, the armature 50 delimits a compression chamber 58, the mantle ofwhich is surrounded by the insulation material 51 and a back part 59 ofthe connector piece 3. The other end of the compression chamber 58 isdelimited by a drive piston 60 which is mechanically linked with a fork62 via a tube 61. A segment 64 substantially near the back end 59 of theconnector piece 3 forms a coil 65 which surrounds the compressionchamber 58, in that the wall of the segment 64 has a continuous radialslit 66 wound like a screw passing through it. The windings are wellinsulated from one another electrically.

A break current which flows through the coil 65 produces a magneticfield in the stator 67 formed by the coil 65, which moves the armature50 towards the flange 55, in the direction of the arrow A. This causesquenching gas contained in the compression chamber 58 to be compressed.The compression chamber 58 acts as an energy accumulator and passes theaccumulated energy on to the fork 62 via the drive piston 60. The timeof energy release can be determined by means of a corresponding releaseof the drive, and can be coordinated with the movement of thecompression cylinder 6 caused by the drive (not shown) via the fork 62and the connecting rods 68. An opening 69 serves as an exit forquenching gas during the movement of the compression cylinder 6.

The gas-blast switch of the present invention as shown in FIG. 3 notonly allows a controllable use of the energy obtained and accumulatedfrom the break current, but also provides a particularly compactarrangement of the compression chamber, which is particularly suitablefor use of a coil as the stator. By means of the design of thepressure-influenced surface 56 of the armature 50 and the surface 70 ofthe drive piston 60, optimal adaptation of the drive support to thestroke and force requirement is possible. Furthermore, it can beprovided that the armature 50 be interconnected in such a way that thecatch can only be released again in the cut-in position of the switch.The release can take place via a guide rod 71 of the positioning spring53. This can be used to prevent the compression chamber 58 from actingcounter to the cut-in movement during cut-in in response to ashort-circuit.

We claim:
 1. An electrical gas-blast switch comprising:a contact deviceincluding a fixed contact piece, a connector piece and a switchingpiece, the switching piece electrically connecting the fixed contactpiece to the connector piece in a contact making position; a compressiondevice for generating a blast of a quenching gas, the compression deviceincluding a compression piston and a compression cylinder; an armature;a stator for generating a magnetic field for causing an axial movementof the armature; and an energy accumulator including a first compressionchamber and a piston-cylinder system, the piston-cylinder systemincluding a first movable element mechanically coupled to the armatureand a second movable element mechanically coupled to the switchingpiece, wherein the armature and the stator are arranged to so that themagnetic field causes the armature to move into a cut-in position, andwherein the energy accumulator is discharged to support the movement ofthe second element and the movement of the switching system.
 2. Thegas-blast switch according to claim 1, wherein the energy accumulator ispositioned within the compression cylinder.
 3. The gas-blast switchaccording to claim 1, wherein the energy accumulator is positionedwithin the connector piece, and wherein gas-blast switch furthercomprises a power take-off piston, the power take-off piston forming thesecond moving element and being positioned on a side of thepiston-cylinder system opposite to the switching piece.
 4. The gas-blastswitch according to claim 3, wherein the stator is a coil.
 5. Thegas-blast switch according to claim 4, wherein the coil includes asegment of the connector piece, the segment including a wall having aradial slit, the radial slit being wound helically through the wall.